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\AUDIO CIRCUITS I have design some power amplifier and many more base on my own basic electronic knowledge. The aim for this circuit is to give DIY fan a chances in making own power amplifier. The circuit originally design by myself therefore some of the result may not satisfied the specifications of HiFi lovers. I use for very cheap material in building the circuit. Please BE CAUTION some of the circuit using our main 230V/110v, please get and advice from an authorize electrician. BEE POWER AMPLIFIER MK II The patience of designing an power amplifier now end. I have finish my latest Bee power amplifier series. I call it Bee Power Amplifier MK II. I is a major upgrade for the old base design, Bee power Amplifier itself. This amplifier is now the top end of my designing goals which is all my experience put on it. After 1 year of tweaking and experimenting on the old Bee power amplifier, I now have great successfully overcome the weakness. I now present my latest design, Bee power Amplifier MK II. Design Details The basic topology still use a same compound power amplifier. This is the core of Bee Power Amplifier. I choose this because is it simpler then a symmetrical topology. It is also a classical topology and the good news for this type of topology it have a better music production then anything else. Below is the upgrade list for my MK II. · Power Supply Filter Capacitor use 1000uF/50V x 40 bypass with 100nF Film foil Capacitors. · Separate 250VA toroidal power supply for each channel. · Higher gauge power cable. · Use fast power transistors in series of two each rails. · Matching all the components. · Change a dc block and input capacitors with non-polarity capacitors bypass each with 100nF. · Change the on off feed capacitors with 10uF/50V non-polarity bypass with 100nF. · Use a low noise signal transistors · 10A IEC with EMI filter. The Bee Power Amplifier MK II run at class AB with a higher quiescent current (800mA). This better for sonic audio production (make it higher so this amplifier can run longer at class A). If a bigger heatsink are used, it can be set safely set at 1.5A. The power transistor is now 2SA1943 and 2SC5200. A new component are added to Bee Power Amplifier MK II for the output stage block. The 47R and 1R resistors is to prevent any internal oscillation for those fast power transistor. A series of power transistor make Bee Power Amplifier MK II have incredible bass production with dynamic result much better then I ever design. This result also came from my top design power supply with a 40 each 1000uF/50V bypass with 100nF design rails. This is better then luxury capacitors available at market which claims to be the best in audio performance. All small signal transistor are now a low noise type. I choose a BC550 and BC560 at this performance and it still cheap at the market. There are now new and better bipolar available. The current source bipolar are super fast type (provide more stability when run at high level). I now use a non-polarity type for global feedback dc blocker capacitor. A dc drain at the blocker can effect audio result. I found that a wrong polarity connection when an electrolytic capacitors are used make the sound worse. Even the polarity is right the audio result never better then to use a non-polarity capacitors. It bring a higher mid respond and smooth. I discover that a non polarity for the input capacitor is far better than an electrolytic type. A class AB feed up capacitor been bypass with a 100nF films capacitors. Anything else is a same design concept on the previous Bee Power Amplifier. You have to read it back if you want to know more. The circuit are shown below. Click to enlarge
Fig 1 - Bee Power Amplifier MK II Test Result A pair of Acoustic Energy Aegis One 88.5dB sensitivity will be the best loudspeaker that I have to get the listening test. A pair of 2.5 meter of QED silver special 25th Anniversary Edition will give a boost to the system. I have to use where a HiFi magazine say to be a 5 star to get the comparison. Bass respond is deep and till the lowest end I ever heard. It is a bass that natural, clean and never over blown at a higher level. My Aegis one loudspeaker where it have a metal mid bass that capable to get over 120W rms and amazingly this amplifier still deliver 'kick bass' even my Aegis started to cut -6dB at 38Hz. This Bee Power Amplifier MK II is around 100W rms. So it is very good to push hard on it. The bass never lack even I push it at the maximum level. The Bee MK II still have enough power for the bass respond. A R&B sound where a very long electronic bass code can easily get into the move when using this Bee MK II. The coherent, precise bass is the result I am searching for and with this Bee MK II have it but nevertheless. Mid respond is natural sound. I shows when I play a song of Sarah Brightman - A question of honors part 2. The female voice is so natural with a opera singer where it tend to be crystal clear with glass breaking sound. Anything small and solidly sound can be hear out. Vocal are warm but not so thin. Sound stage follow under it natural phenomenon. A tiny sound produce tiny or small alarm clock it can easily hear that is never even heard before. This is solid state amplifier that have a great details in amplification. Say sorry to a poor and faulty recording process because Bee MK II will not immerse this kind of problem. It never lie to me for the sound stage. One more thing It, I wonder who knows the real sound stage without see it??? Overall the sound for me still far perfect. I found that it became to be lost control on the mid and treble when it run at maximum level. What do you expected from a simple solid state power amplifier. This Bee MK II is better then any amplifier I ever build before. It kick-off the Kenwood 3020 (sorry this is only my opinion) for the mid respond and bass. This Bee MK II is natural smooth treble but still not to smooth . I hate over smooth sound because it may sound badly when I play an opera music or live songs. The transparency of this Bee MK II came out from the RM170 QED Silver 25th Anniversary Special Edition. I do not test it with a non hifi speaker cable. The stability of the Bee MK II still moderate because it will a small hiss at higher volume but the 89dB loudspeaker might not enough sensitivity. I have to change around 90dB for a better result. The life performance under moderate level. Maybe there are something not match here for soundstage. I have to find another life recording music. The speed is excellent with clearly treble plus extended large bass with under control at a medium volume level still give this Bee MK II an advantage to build. I am very confident on this Bee MK II. I have spent all my money and knowledge on this. The result not perfect but for me it is better to spent my money then buying an expensive power amplifier on the market. This is 100% my own design and I am very confident it will bring you big smile if you built it. The good is I am surely it can give a big smile on your face when you build it. Better build one DIYER. The Cost The cost is higher because I using a high quality component. I have to match all the power transistor. Only 8 are choose from 16 of the power transistors. The resistors is 5% and all of it using a same value from my Digital Multimeter set. Thus only 40% of total 80 resistor meets the requirement. I do not use a 1% resistors. I am to lazy for buying it. Well a same cost for a 5% resistors indeed after I omit the unused resistors. The Power supply section is using a 250VA toroidal for each one channel which cost me RM120 each. A 40 pieces of 1000uF/50V capacitors bypass each with 100nF really make this amplifier costly. The big heatsink is at RM44 and still smaller to cool down if the IQ set at 1A. I hate to put a cooling fan which is nosier to sound. Maybe next now Bee MK III will be a bigger heatsink. I think I will try another type of amplifier. Single end class A is in my mind. Zen have it but I am searching a better then that. State of the Amplifier where are the cost all DIY me and my big mind. I have invest about RM1200 for this amplifier overall. I am about to sell this Bee Power Amplifier MK II at RM1800 because of the performance. See and test for yourself. I really have to sell for my study fees next semester and I am really have to sell it even I really like it.
Fig1- Bee Power Amplifier MK II (front view)
Fig 2 - Bee Power Amplifier MK II (40 pcs Power Caps Bypass with 100nF)
Fig 3 - Bee Power Amplifier MK II (Rear View with IEC EMI filter unit) Note - I do not have a monitoring tools like audio spectrum analyzer, THD meter or anything else to check the measurement. What I just do is listening hourly and then step by step upgrading the component to get a better sound result. Therefore I do not shows the THD measurement, Damping factor or IMD quantity. What most you trust, a data value or your own ears. My opinion is better trust on yourself. Nanhifi May 2004 |
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